Putative cell membrane targets will be examined as possible mediators of the cytotoxicity of anthracycline anticancer drugs such as Adriamycin. Cell membrane-bound protein kinase C (calcium-phospholipid-dependent protein kinase) and its associated phorbol diester receptor will be measured for its activity and ability to bind radiolabeled phorbol diester. The ability of phorbol diesters to alter the cytotoxicity to human colon carcinoma cell line HT-29 and promyelocytic leukemia HL-60 will also be measured by a clonogenic assay. Possible cellular targets such as the phosphorylation of microfilaments and other peptides associated with the activity of protein kinase C will be examined electrophoretically using immunochemical procedures.